From the Guidelines
Azithromycin is generally considered safe during pregnancy when medically necessary, as evidenced by its classification as FDA pregnancy category B and supported by recent studies 1.
Key Points to Consider
- Azithromycin is often preferred over other antibiotics for treating certain infections during pregnancy, including respiratory tract infections, chlamydia, and other bacterial infections.
- The typical adult dose is 500 mg on day one, followed by 250 mg daily for 4 more days for most infections, though single-dose regimens (1 gram) may be used for certain conditions like chlamydia.
- When prescribed during pregnancy, the benefits of treating the maternal infection typically outweigh potential risks to the fetus.
- Azithromycin works by inhibiting bacterial protein synthesis, and its pharmacokinetic properties allow for once-daily dosing with good tissue penetration.
- While generally safe, it should still only be used during pregnancy when clearly needed, and the healthcare provider should weigh the benefits against any potential risks for the individual patient's situation.
- A recent study suggests a very low risk of hypertrophic pyloric stenosis in infants exposed to macrolides during the first 13 days of breastfeeding, but not after 2 weeks 1.
Important Considerations
- The healthcare provider should be cautious when prescribing azithromycin to patients with impaired hepatic function, as it may require dose adjustments.
- Patients should be advised not to take azithromycin and aluminum- or magnesium-containing antacids simultaneously, as the latter reduces the rate of absorption of azithromycin.
- Monitoring of patients is advised when azithromycin is used concomitantly with agents metabolized by the cytochrome P450 enzyme system and with other drugs for which the pharmacokinetics change.
Summary of Evidence
- Studies have consistently shown that azithromycin is safe and effective for use during pregnancy, with minimal risks to the fetus 1.
- The most recent study, published in 2020, confirms that azithromycin is probably safe for use during pregnancy and breastfeeding, with a low risk of adverse effects 1.
From the FDA Drug Label
Pregnancy Teratogenic Effects. Pregnancy Category B Reproduction studies have been performed in rats and mice at doses up to moderately maternally toxic dose concentrations (i.e., 200 mg/kg/day). These doses, based on a mg/m2 basis, are estimated to be 4 and 2 times, respectively, the human daily dose of 500 mg. In the animal studies, no evidence of harm to the fetus due to azithromycin was found. There are, however, no adequate and well-controlled studies in pregnant women Because animal reproduction studies are not always predictive of human response, azithromycin should be used during pregnancy only if clearly needed.
The safety of Azithromycin in pregnancy is categorized as Pregnancy Category B.
- Key points:
- No evidence of harm to the fetus was found in animal studies.
- There are no adequate and well-controlled studies in pregnant women.
- Azithromycin should be used during pregnancy only if clearly needed 2.
From the Research
Safety of Azithromycin in Pregnancy
The safety of azithromycin in pregnancy has been investigated in several studies, with conflicting results.
- Some studies have reported increased risks of spontaneous miscarriage, major congenital malformations, cardiovascular malformations, digestive system malformations, preterm birth, and low birth weight associated with prenatal azithromycin exposure 3.
- However, other studies have found no significant differences in complications for women or infants exposed to azithromycin compared to those treated with other regimens 4, 5.
- A study comparing azithromycin and erythromycin in the treatment of cervical chlamydial infection during pregnancy found that azithromycin was better tolerated and had a similar cure rate to erythromycin 6.
- Another study found that gestational exposure to azithromycin was not associated with an increase in the rate of major malformations above the baseline of 1-3% 5.
- A randomized controlled trial comparing the pharmacokinetics of 1-time vs daily dosing of azithromycin in the setting of preterm prelabor rupture of membranes found that daily dosing maintained higher amniotic fluid concentrations and more consistently greater than common minimum inhibitory concentrations over 8 days compared to 1-time dosing 7.
Adverse Outcomes
The available evidence suggests that azithromycin use in pregnancy may be associated with some adverse outcomes, including:
- Spontaneous miscarriage
- Major congenital malformations
- Cardiovascular malformations
- Digestive system malformations
- Preterm birth
- Low birth weight However, the current evidence is not conclusive, and more research is needed to fully understand the safety of azithromycin in pregnancy 3, 4, 5.
Clinical Use
Azithromycin should only be used during pregnancy when clinically indicated, and if the benefits of treatment are expected to outweigh the potential risks 3.